Don't Cut Wild Grapevines to Reduce
Grape Berry Moth Populations
The native grape berry moth is a primary pest of eastern North American
vineyards. Larvae of this insect feed on the developing grape clusters,
reducing yields, introducing pathogens and infesting grapes at harvest.
Growers have relied on insecticides and more recently, on mating disruption
of adults, to manage the damage caused by the three generations that occur
in Ontario.
Grape berry moth occurs on both wild and cultivated grape. Vineyards
are often located near woodlots where wild grapevines grow, which provides
unmanaged habitat where grape berry moth can reproduce. Growers and pest
management specialists have found that grape clusters at vineyard borders
are typically more infested than those growing within the interior. Therefore,
cutting wild grapevines to reduce infestations has been suggested as a
pest management strategy. Similar programs targeting wild hosts and abandoned
orchards have been very successful for other insect pests such as the
codling moth in apples, but until recently, the impact of cutting wild
grape on pest pressure by grape berry moth had not been studied.
Researchers in Michigan (Jenkins and Isaacs, 20071) attempted
to evaluate the effects of alternate host removal on grape berry moth
infestation levels by eliminating all wild grapevines within 60 m of adjacent
vineyards. But what they found was that this very intensive work had little
impact on the level of infestation at harvest. One of the reasons for
this may be due to the ability of moths to move between habitats. Studies
using pheromone traps show that grape berry moth males can fly more than
100 m between woodlots and vineyards; females may also move these distances
in search of suitable hosts on which to lay their eggs.
So what is the message here? In short, growers should not invest the
time and labour required to cut wild grapevines in woodlots near their
vineyards. Wide-scale, county level removal of wild grape might have some
impact on pest numbers; however, this could also have negative impacts
on the overall the health and diversity of the woodlot community, including
numbers of natural enemies for grape berry moth and other insect pests.
A better solution to managing grape berry moth infestations is to invest
in regular scouting, making timely application of insecticides or adopting
area-wide mating disruption of adults.
1Paul E. Jenkins and Rufus Isaacs. 2007. Cutting wild grapevines
as a cultural control strategy for grape berry moth (Lepidoptera: Tortricidae).
Envir. Entomol. 36(1):187-194.
